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Primary: Set value IP = 630 A,
Secondary: Set value IP = 5.25 A, i.e. (630 A/600 A) X 5 A.
The set time multiplicator T Ip Time Dial (address 2642) or T Ip Dir. (address
2690) results from the grading coordination chart defined for the network. For the use
as emergency overcurrent protection shorter delay times make sense (one grading
time step above instantaneous tripping), since this function is to work only in case of
an interruption of the data communication for the differential protection.
The time multiplicatorT 3I0p TimeDial (address 2652) orT 3I0p Dir. (ad-
dress2695) can normally be set shorter, according to a separate time grading sched-
ule for ground currents. If only the phase currents are to be monitored, set the pickup
value of the earth current stage to ∞.
In addition to the current-dependent delays, a fixed time delay can be set, if necessary.
The setting T Ip Add (address2646 ) or T Ip Add Dir. (address 2692) for phase
currents and T 3I0p Add (address 2656 ) or. T 3I0p Add Dir. (address 2697)
for earth currents add to the times of the set characteristics.
The parameter I(3I0)p Tele/BI (address 2670) or IPDir.Telep/BI (address
2698) determines whether via the binary input „>O/C InstTRIP" (No 7110) the
delay T Ip Time Dial (address 2642) or T Ip Dir. (address 2690) including
additional delayT Ip Add (address 2646) or. T Ip Add Dir. (address 2692) and
T 3I0p TimeDial (address 2652) or T 3I0p Dir. (address 2695) including ad-
ditional delay T 3I0p Add (address 2656) or T 3I0p Add Dir. (address 2697)
can be bypassed. The binary input (if allocated) is applied to all stages of the time-
overcurrent protection. With I(3I0)p Tele/BI = YES or IPDir.Telep/BI = YES
you define that the IP>stages trip without delay after pickup if the binary input was ac-
tivated. For I(3I0)p Tele/BI = NO or IPDir.Telep/BI = NO the set delays are
always active.
Instantaneous tripping by the operational auto-reclosure function should only be
chosen if the overcurrent protection is set to emergency function. Since the differential
protection guarantees a fast and selective tripping with or without auto-reclosure, the
overcurrent protection as a back-up protection may not perform a non-selective trip,
even before auto-reclosure.
If the IP>stage, when switching the line on to a fault, is to trip without delay or with a
short delay SOTF Time DELAY (address 2602, see above under margin heading
„General") the parameter I(3I0)p SOTF (address 2671) or IP Dir. SOTF (ad-
dress 2699) is set to YES. We recommend, however, not to choose the sensitive
setting for the switch on to a fault function as energizing of the line on to a fault should
cause a large fault current. It is important to avoid that the selected stage picks up due
to transients during line energization.
Time Overcurrent
In the case of the inverse overcurrent stages, various characteristics can be selected,
depending on the ordering version of the device and the configuration (address 126),
Stages I
, 3I
,
P
0P
With the ANSI characteristics (address 126 Back-Up O/C = TOC ANSI), the follow-
I
ger, 3I
ger for
P
0P
ing options are available at address 2661 ANSI Curve:
inverse-time O/C
protection with
Inverse,
ANSI characteristic
Short Inverse,
Long Inverse,
Moderately Inv.,
Very Inverse,
Extremely Inv. and
7SD610 Manual
C53000-G1176-C145-4
2.9 Backup Time Overcurrent Protection
115
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